This invention relates to electronic control circuitry and more particularly relates to apparatus for controlling the duty cycle of a signal.
Manufacturers of electronic musical instruments have long sought a means of accurately adjusting the duty cycle of a tone generator used to create different types of orchestral sounds requiring different harmonic spectrums. For example, experience has shown that a tone signal with a 50% duty cycle is useful for producing a clarinet-type sound and a tone signal with a 12.5% duty cycle is useful for producing a string-type sound. One musical instrument capable of using such a circuit is described in detail in the copending application of the present applicant, as well as George R. Hall and Jack C. Cookerly, entitled "Orchestral Accompaniment Techniques", which is incorporated by reference.
Accordingly, it is an object of the present invention to provide a circuit for accurately controlling the duty cycle of an input signal irrespective of changes of frequency of the input signal.
Another object of the invention is to provide a circuit of the foregoing type which is capable of accurately adjusting the duty cycle of the resulting output signal with respect to the input signal.
Still another object of the invention is to provide a circuit of the foregoing type in which the components are arranged to avoid changes in the duty cycle due to changes in conditions, such as temperature and component values.